Patients who have breathing difficulties are conventionally provided breathing assistance using mechanical ventilators. These devices are generally expensive and out of reach of a large portion of the population, particularly in economically disadvantaged countries. These devices also require substantial training and expertise to operate and maintain. Further, these devices do not provide the user the ability to set and vary upper limit of safe positive pressure that is patient specific and commensurate with the peak inspiratory pressure levels set during ventilation in an easy and less expensive way using a fluid column.
In recent years, there has been increasing interest in the development of breathing assistance devices that are less expensive. U.S. Pat. No. 8,499,759 discloses the use of a two-way valve in a pressure regulating breathing assistance apparatus wherein the valve is placed intermediate two pressure control conduits that are submerged at varying lengths in a single container containing a fluid. In such apparatus, depending on the size of the valve, back pressure is generated whereby the pressure of gas at a patient interface may be higher than the pressure set using one of the control conduits, but not the other. This back pressure, if not correctly accounted for, has important treatment and safety implications if the device is used on a patient. Further, when two pressure control conduits are located in the same container, the interaction between the two conduits in operation may impact pressures at a patient interface.
There is a significant need to provide a respiratory assistance apparatus that is easy and less expensive to make, operate and maintain, and has high-positive-pressure safety feature that is simple, reliable and easily adjustable relative to the desired patient-specific inspiratory pressure level.